Tip growth

Morre DJ. Endomembrane system of plants and fungi, in Tip Growth in Plant and Fungal Systems (Heath B, ed.), Academic Press, San Diego, CA, 1990. 

Growth Mechanisms. Growth mechanisms have been investigated, andsev-eral theories have been proposed. There are two general models that are used to explain catalytic synthesis of nanowires or nanotubes. The first is called tip growth, in which... 

Evidence for Tip Growth. The evidence for tip growth can be found from the images which directly show that nanowires are connected to metal catalysts. Figures 10.18 and 10.19 show two types of SiNW, one straight and one coiled. This clearly indicates that nanowires were grown from the tip. 

As presented above, we have observed SiNW with nanoparticles at their ends, suggesting tip growth. The Co in the samples seemed to have a composition different from Co metal and crystalline CoSi2, as suggested by the XAS experimental results. Undetectable amounts of carbon were found in those SiNW, and large quantities of SiNW can be made with the current method. Thin films of SiNW can now be separated from the substrate, making it possible to directly handle mass quantity SiNW. 

However, it is unclear what the growth mechanisms are because no Si feedstock was fed in the gas form, which is required for the tip-growth model to work. In the following, we will discuss the composition and growth mechanisms of the nanowires made in this work, and show that the Co nanoparticles may play a dual-catalytic role by helping form gaseous silicon species and catalyze the growth of Si-based nanowires. 

Our experiments have shown that hydrogen is critical for growth. The required presence of both hydrogen and metal catalysts, and the virtual absence of silicon vapor suggest that totally new reaction paths assist in the growth of these nanowires under the conditions studied. If silicon does not come directly from the wafer substrate, then it is required to become airborne in some form, as in the CVD production of SiNW, thus enabling tip growth. 

It is noteworthy that longitudinal microtubules were also observed in the root hairs of some higher plants which show tip growth (46-48). 

Whiskers can be formed from a variety of materials, as illustrated in Table 5.9, but there are only two general methods for forming them basal growth and tip growth. 

The process of differentiation that transforms primary cells into secondary cells is only partially understood. In such thick-walled cells as tracheids, fibers, and vessels in mature tissues, the greater part of the wall is made up of secondary thickening deposited after expansion of the primary wall has stopped. In cells that show localized growth (for example, tip growth), the secondary wall may well start to form in areas removed from the growing zone, while the latter is still active.2... 

Suppose that the capillarity effect of curvature on solubility is included in Exercise 22.3. Describe qualitatively what happens to the tip growth rate as the tip radius decreases without limit. 

Betaines (hypaphorine and oxyneurine) Erythrina sp. and Lycium barbarum Stimulate at low concentration and inhibit at high concentration of lentil root tip growth 177... 

Bartnicki-Garcia, S. (2002). Hyphal tip growth outstanding questions. In Molecular Biology of Fungal Development, ed. H. D. Osiewacz. New York Marcel Dekker, pp. 29-58. 

Recently, genotypic variation in mature cotton fiber surface components, presumably from the cuticle, has been reported [51]. In the cytoplasm, smaller vacuoles coalesce into one large central vacuole leaving only a thin ribbon of cytoplasm between the vacuole membrane and the cellular membrane (plasmalemma). Organelles are distributed in the cytoplasm in a manner that is consistent with a model for cell expansion occurring by intercalation rather than tip growth [52,53]. The random orientation of cell wall polymers in the primary cell wall... 

Figure 11 Tip-growth and extrusion mechanisms of carbon filament growth. (Ref. 58. Reproduced by permission of Elsevier)...

J/m. In turn these values of F produce substantial predicted differences in craze growth kinetics. Substituting these values into Eq. (7) the craze tip velocity at constant S, = 100 MPa is predicted to decrease by a factor of 10 from PTBS to PC (values for h of 10 nm and for n, the power law exponent, of 17 are assumed for both) or equivalently the value of Sj to give the same craze tip growth rate increases by a factor of 2.8. Since the measured stress S at the craze tip in PTBS is 27 MPa, the craze tip stress in PC is predicted to be 74 MPa, well above its... 

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